Biographies of Muhammad, the founder of Islam, used to develop the hadith. The value of the sira have been both to help develop Muslim Law, Sharia, and to facilitate the interpretation of the Koran.Sunna, the examples, the deeds, sayings and unspoken approval of Muhammad, is defined as the sira and the hadiths together.Sira may be translated with "way of acting", which largely corresponds with the meaning of "biography", the other term it can be translated into.Sira represents the basis for the hadith, but without validatinh the stories recorded, by a chain of transmitters, isnad, as is the case with the hadiths. The reason why siras would come without this sort of validation may be explained that they didn't serve as important a role as the hadiths, which were used in the development of Muslim Law. Still, many of the earliest sira actually had an isnad, causing problems with the demarcation between the two disciplines.Before the collection of the siras, the traditions were held up by qussas, professional story-tellers.The oldest survivng sira is the "Biography of God's Messenger" by Ibn Ishaq, written around 780, or 150 years after Muhammad's death. The achievements of Ibn Ishaq would by the writers of the hadiths be deemed very unreliable, much because of an uncritical acceptance of stories with bad isnad. It is much from both their needs to use his information and distancing themselves from his technique, that the actual division between sira and hadith came to be.There had been numerous siras written before Ibn Ishaq, where Urwah ibn az-Zubayr seems to have compiled the first sira around 700, about 70 years after the death of Muhammad.The primary concern of the earliest siras were to fix the regular practice of worship, aided by great interest in the society of the near history of great wars and conquests.Both Mulisms in general, Muslim scholars and a majority of Western scholars see the sira as reliable sources to the life and time of Muhammad. Yet, the validity has been challenged by some scholars, like Henri Lammens early in the 20th century, who alleged that all information about Muhammad prior to 610, was unsubstantiated.Other early siras are those of Ibn Hisham and at-Tabari.It is from the sira we learn about the Satanic Verses, which is dealt with by at-Tabari.'Sira' is sometimes used in place of 'sunna' and 'hadith' and vice versa. Although this is incorrect, it still reflects their closeness in meaning.